Eight agents have been demonstrated to possess immunoadjuvant activity (5 chemicals and 3 biologicals). In vitro studies with pyran copolymer, glucan, and purified interferon show that they directly activate naive macrophages to exert a tumoricidal effect. A marked correlation has been demonstrated for the capacity of pyran copolymer and glucan to enhance antitumor resistance in the host and their ability to activate macrophages in vitro. Histopathological studies show that pyran treatment not only increases macrophage function, but also mobilizes macrophages to migrate to the primary and disseminated tumor sites exerting tumoricidal effects. Activation of macrophages by polyanion adjuvants may be mediated through an interferon mechanism rather than a cellular metabolic product or as yet unidentified material. Polyanions are interferon inducers. Interferon per se activates macrophages indicating that interferon may be acting as a lymphokine. BIBLIOGRAPHIC REFERENCES: Schultz, R.M., Papamatheakis, J.D., Luetzeler, J., Ruiz, P., and Chirigos, M.A.: Macrophage involvement in the protective effect of pyran copolymer against the Madison lung carcinoma (M109). Cancer Research 37: 358-364, 1977. Schultz, R.M., Papamatheakis, J.D., and Chirigos, M.A.: Direct activation in vitro of mouse peritoneal macrophages by pyran copolymer (NSC-46015). Cellular Immunology 29: 55-61, 1977.